1. Field of Invention
This invention relates to an improvement in disc brakes in which relatively stationary and rotatable surfaces are brought into frictional engagement by the axial separation of an actuation plate and a cooperating pressure plate. Between the actuation plate and the pressure plate are arranged angularly spaced balls which work in complimentary ramps positioned within depressions in the adjacent surfaces of the plates.
2. Description of the Related Art
It is known in the art to provide a disc brake in which relatively stationary and rotatable surfaces are brought into frictional engagement by axial separation of a pair of pressure plates. Typically, angularly spaced balls are arranged and work within inclined depressions in adjacent surfaces between the pressure plates to separate the pressure plates. The disc brake has rotatable surfaces that are formed on discs splined, or otherwise keyed, for rotational movement on a rotatable shaft. The discs provide the rotatable surfaces and are axially slidable on the shaft. Stationary surfaces are formed by end walls of a housing enclosing the discs and the pressure plates.
In a spreading-type multiple disc brake, the pressure plates are usually centralized within a housing. The axial separation of the plates is accomplished by providing a means for initiating angular movement of the pressure plates relative to each other in order to separate the pressure plates. The separation of the pressure plates causes the other surfaces of the brake discs to come into frictional engagement. The pressure plates are then rotated by the rotating surfaces until one plate abuts a stop on the housing. Generally, a cam mechanism causes the axial separation of the pressure plates and thereby engagement of the other brake discs with each other. The cam mechanism has balls operated in conjunction with ramps in adjacent surfaces of the plates. A brake applying mechanism moves the pressure plates angularly relative to each other, and in opposite directions, thus engaging the balls or rollers with the ramps defined by the recesses. This causes the pressure plates to move apart and into engagement with friction discs. The friction, or rotating discs, are then urged into engagement with the stationary braking surfaces.
Often a disc type brake device is mounted on a shaft projecting outside the housing. This makes the brake devices vulnerable to damage due to corrosion and extraneous matter such as dust and dirt. Such brake devices may therefore require excessive maintenance.